The present invention relates to water treating systems and, more particularly, to a water treatment system, the efficacy of which may be periodically regenerated, and an electronic control for such a treatment system.
Water treatment systems may typically include a treatment tank which is filled with a resin material, such as zeolite, forming a resin bed through which untreated water is directed. In the case of a zeolite resin bed, hard water passing through the treatment bed will experience an ion exchange process in which the sodium ions are exchanged for hard metal ions in the water. The water treating efficacy of the zeolite bed will be gradually reduced and, after a predetermined quantity of water has been treated, the ion exchange process will no longer take place. It is possible to generate the zeolite bed, however, by passing a salt brine solution through the bed to reverse the ion exchange process. The maximum period of time between successive regeneration operations is dependent upon both the hardness of the water and the quantity of water which is treated.
The operation and regeneration of prior art water treatment systems have generally been controlled by simple timer arrangements in which a regeneration cycle is initiated at a predetermined time, usually late at night, every several days. Such a regeneration control scheme results in regeneration at times which roughly approximate those at which regeneration is actually required. During periods of unusually high water usage, the zeolite bed effectiveness may be depleted substantially before regeneration occurs, thus resulting in only partially treated water being supplied by the softener. Conversely, during periods of time in which little water is used, regeneration will occur too frequently and brine solution will be wasted.
The brine which is used during regeneration is stored in a brine tank to which salt is periodically added. Should the quantity of salt in the brine tank be reduced substantially without additional salt being added, the brine solution used for regeneration may be sufficiently concentrated to restore the water treating efficacy of the resin bed. Prior art control devices made no provision for altering the regeneration cycle to compensate for this condition. Additionally, refilling the brine tank after regeneration has typically been accomplished by applying water through a control valve arrangement for a predetermined period of time. Should this valve arrangement malfunction, the brine tank might overflow. No provision has been made in prior art systems to detect or correct this condition.
Several prior art controls have been designed to minimize brine solution waste, while providing more frequent regeneration during periods of heavy water use. One such control is shown in U.S. Pat. No. 3,176,844, issued Apr. 6, 1965, to Nelson, in which the resistance between electrodes in the water softener treatment tank is measured to determine when the softening capability of the zeolite bed has been depleted. When depletion occurs, the regeneration operation is initiated.
Another technique is shown in U.S. Pat. No. 3,687,289, issued Oct. 29, 1972, to Tischler, in which a small fraction of the treated water is metered into an adjustable water storage chamber. The water in the chamber is periodically directed to the brine storage tank and when the liquid level in the brine storage tank reaches a predetermined height, a timer is actuated. The timer will cause regeneration of the system at a selected time during the following 24-hour period.
A control system for controlling regeneration of a water softener system is disclosed in U.S. patent application Ser. No. 779,097, filed Mar. 18, 1977, by Davis, and assigned to the assignee of the present invention. The Davis application discloses an electrical water softener control which includes a flow meter in the water line providing a pulse output of a frequency proportional to the flow rate of the water treated by the softener. A counter circuit initiates regeneration at a predetermined time of day next occurring after a quantity of water equal to the treatment capacity of the system, less an average 24-hour supply, has been treated. The circuit will also initiate regeneration immediately, should a quantity of water equal to the treatment capacity of the system be treated.
The control systems which have monitored the level of brine solution in the brine tank of a water softener have generally relied upon mechanical or electromechanical level sensors. U.S. Pat. No. 2,067,808, issued Jan. 12, 1937, to Zimmerman, et al, for instance, discloses a softener in which the level of brine solution in the brine tank is sensed by means of a simple float arrangement. U.S. Pat. No. 3,130,154, issued Apr. 21, 1964, to Heskett, discloses a fluid level control arrangement for the brine tank of a softener in which air is trapped in a chamber by rising brine fluid and, when the brine solution reaches a predetermined level, actuates a pressure-responsive electrical switch. U.S. Pat. No. 2,919,805, issued Jan. 5, 1960, to Nickols discloses a water softener having a brine tank in which electrical probes are used to detect when the solution in the brine tank has reached the lowest desired level during regeneration and also to detect when the brine tank has been refilled to a selected level during regeneration. The control circuit in the Nickols patent, however, includes a relatively simple electro-mechanical timer device.
It is seen, therefore, that a need exists for a water treatment system and a control therefor in which operation and regeneration of the system are monitored and controlled electrically by a control device providing maximum flexibility in operation of the system. Such a control arrangement should permit both the timing and sequencing of the system operations to be controlled selectively and, further, should provide various error indicating and correcting operations in the event of a malfunction of the treatment system.